Search for the Critical Point of Quantum Chromodynamics (QCD)

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Relativistic nucleus-nucleus collisions create a short-lived compound system (the Hagedorn fireball) of fused, high energy density matter, the properties of which being reflected in a multitude of physics observable as imbedded in the experimentally observed final state. A recent breakthrough in non-perturbative lattice Quantum Chrome-dynamics (QCD) has led to detailed predictions concerning the parton-hadron coexistence line in the QCD phase diagram which, in particular, seems to exhibit a critical point in the (, T-diagram. Moreover (pending further lattice technical refinement) this point appears to occur in the interval 300 ( (B ( 450 MeV that corresponds to the lower energy domain of the CERN SPS experiments (7 ( ( 10 GeV) that ended in 2002. The renewed interest in this energy interval leads us to propose revisting the corresponding NA49 data (Pb+Pb at various SPS energies) which either have not been previously analyzed, or are not yet in their final form. The physics of the critical point (and the first order parton hadron phase transition occurring at ( > (crit) suggest event by event fluctuation analysis, e.g. of the eventwise transverse momentum < pT >, the pion and kaon multiplicity density, as well as several ratios of nonstrange to strange particle production like the eventwise K/( and K/p ratios. The large acceptance and the high hadron discrimination power of NA49 (which ran until 2002) make these data analysis particularly promising.